1. Field of the Invention
The present invention relates to a method for modifying a polymer, more specifically relates to a method for reacting a polymer, a compound having a nitroxide radical in the molecule thereof, a radical initiator, and a radical polymerizable monomer in a non-solvent system so as to graft the radical polymerizable monomer to the polymer.
2. Description of the Related Art
Butyl rubber, ethylene-propylene polymer (EPM), and other thermoplastic polymers, or diene-based rubber or polypropylene, polyethylene, and other thermoplastic resins are low in polarity, and therefore, there are the problems that the compatibility with a polyamide, polyester, or other resins is low and the bondability thereof to glass etc. is inferior.
For example, Japanese Patent Publication (A) No. 2004-182926 and Japanese Patent Publication (A) No. 2004-108986 have proposed to introduce a functional group into a polymer with TEMPO (i.e., 2,2,6,6-tetramethyl-1-piperidinyloxy radicals) or the derivatives thereof and a radical initiator. However, polymers desirably have various functional groups, depending on their applications, and therefore there are problems that it is necessary to synthesize various types of TEMPO derivatives in advance and the cost becomes high. Further, U.S. Pat. No. 4,581,429 discloses a method for reacting a nitroxide radical compound with a polymer in a solvent system, followed by adding a monomer and performing a graft reaction. In the first stage reaction where the nitroxide radical compound is reacted with and grafted to the polymer, it is necessary to use a high hydrogen abstraction radical initiator. In the case of a solvent system, there are limitations to the reaction at a high temperature, and therefore a radical initiator having a high hydrogen abstraction even under moderate conditions has to be used, but such a radical initiator is a very dangerous compound and difficult to handle. Further, since the hydrogen abstraction from a solvent lowers the reaction efficiency, in U.S. Pat. No. 4,581,429, a solvent replacing all of the hydrogen with chlorine is used, but such a solvent causes a high load on the environment. Further, a reaction efficiency of a solvent system is lower than a non-solvent system. Therefore, since the introduction rate of the TEMPO moiety in the first stage reaction is low, there is a problem that the introduction rate of the functional group in the second stage graft reaction starting from that moiety also becomes low.